GRAPE BIOLOGY Rebecca Harbut Dept of Horticulture, UW-Madison VITACEAE • Mostly woody, tree-climbing vines • Tendrils and inflorescences opposite the leaves • 12 genera within the family – Vitis – Ampelocissus – Clematicissus – Parthenocissus (Virginia Creeper) – Ampelopsis – Cissus (Kangaroo vine) GENUS VITIS • 60 species of grape – 30 species native to North America • Two subgenera: – Euvitis (38 chromosomes) • Grapes adhere to cluster – Muscadinia (40 chromosomes) • Grapes fall off cluster as they mature GENUS VITIS • Euvitis – Vitis vinifera European wine grapes » Over 5000 cultivars » 90% of world grape production – Vitis labrusca American species, fox grape – Vitis riparia American species, ‘coldclimate grapes • French-American hybrids – ‘Marechal Foch', ‘Vidal Blanc', ‘Chambourcin', and ‘Seyval'. • Muscadinia – Vitis rotundifolia Muscadine grapes (grown in SE USA, lack cold hardiness EUROPEAN VS. AMERICAN Vitis Vinifera • Cold tender • More upright growth • Phloxera susceptible Vitis Labrusca & Vitis Riparia • More cold hardy • More trailing growth • More vigorous growth GRAPE USE IN U.S. Wine - 50-55% Raisins - 25-30% Table - 10-15% Juice, jelly, etc. - 6-9% Canned - < 1% GRAPE ANATOMY ROOTS • Grapes have tap root system – Main tap root with lateral roots • Most absorption (nutrients and water) carried out by root tips and root hairs – Soil conditions are critical (proper soil test and site prep) • Vesicular arbuscular mycorrhizae (VAM) – Most associated with plants in low P soils – Most grapes have VAM infecting roots ROOTSTOCKS • Primary reason - Phylloxera resistance • 3 species used: 1) Vitis rupestris: A native of the eastern United States which provides vigor 2) Vitis berlandieri: A native of the dry southwestern United States which provides drought tolerance. 3) Vitis riperia: A native of the northeastern United States which provides cool weather tolerance. Photo: OSU OWN ROOTED VS. ROOTSTOCKS • Grafted vines can be more expensive – Increased time in nursery – More labor • Own rooted can be better in areas prone to winter damage as new growth can come from established roots • Rootstocks can be used to compensate for less than ideal sites ROOT GROWTH AND IRRIGATION • Root growth is critical for vine establishment • Irrigation during can allow for improved root establishment • Deep watering encourages roots to move down into the soil profile TRUNK • Primary support structure • Important in carbohydrate storage • May be single or split CANES, CORDONS AND SHOOTS… OH MY! • Cordon-permanent stem – Trained horizontally – Not all systems have cordons • Cane – One year old shoot – SPUR- Canes pruned to 2-3 buds • Shoot – Current seasons growth – Bear fruit clusters One year old cane Shoot Cluster Tendril BUDS INITIATION • Primordia- undefined tissue with potential to develop into a defined structure • Primordia can become: tendril, shoot, inflorescence – Temperature, vine vigor, light affect cluster size and number • Primordia initiate when only few inches from growing shoot tip BUDS DIFFERENTIATION • Differentiation- process in which primordia become committed to develop into a specialized tissue – Tendril, inflorescence, shoot • Secondary buds differentiate later – Important if primary bud is killed Primary Bud Secondary Bud Tertiary Bud TENDRILS • Specialized lateral branches – Derived from same undifferentiated primordia as flowers • • • • Grow away from the light Become lignified Allow plant to invest less in structural trunk If tendril does not latch onto anything it will wither and die • Tendrils have determinate growth FLOWERS • Small 1/8 inch, indiscrete • 5 sepals, petals, stamens • Superior ovary – 2 locules/2 ovules per locule • Cultivated grapes have perfect flowers – Some wild have male and female flowers – Evidence that cross pollination increases size Fused petals = calyptra INFLORESCENCE/CLUSTER • Panicle inflorescence – Inflorescence usually on 3rd or higher node – # of inflorescence (clusters)/shoot varies by: • Management, cultivar, environment • 0 to 5 (or more) HARDINESS • Vinifera 0 to -10°F bud injury <-10°F trunk injury • French hybrids -10°F bud and trunk injury -20°F kill buds and trunks • American types -20°F would cause crop reduction FLOWERING • Grapes flower long after bud-break • Shoot must develop enough leaves to support fruit development • Flowers open when shoots have 15-17 nodes • Length of flowering period dependent on environment POLLINATION • Wind pollinated – Weather dependent • Fertilization dependant on weather – Pollen tube must grow down through style (highly temperature dependent) – Cool weather during fertilization decreases fruit set FRUIT SET • Fruit Set- percent of flower buds that develop fruit • Auxins (hormone) are released from pollen tube which stimulates growth of ovarian tissue • Factors affecting fruit set: – – – – – Temperature Light (photosynthesis) Stored carbohydrates Water Nutrients ~ primarily Zn and B FRUIT • Grapes are true berries – primary tissue from ovarian tissues • Berry size influenced presence or absence of seeds and then seed mass – V. vinifera- 1-2 seeds – V. lubrusca >2 seeds • Seedless grapes – Most not really seedless (stenospermocarpic) – Seeds form, but abort – Still enough hormone production to stimulate large berry growth – Truly seedless (parthenocarpic) have smaller berries BERRY COMPOSITION • 75-85% water • 15-25% sugar • 0.5-1.0% organic acids (malic, tartaric, citric) • 0.25% pectin • Secondary metabolites BERRY COMPOSITION: SECONDARY METABOLITES • Components that make grapes distinctive • Not essential for survival of the plant • Thousands have been identified, likely many more – Phenolics, anthocyanins, flavenoids • Synthesis is genetically controlled • Influenced by: – Environment, plant age Phase I Phase II Phase III BERRY DEVELOPMENT: PHASE I (0-40 DAF) • Phase I- cell division and expansion – 17 cells to 200,000 (600,000 cells at veraison) – No carbohydrate accumulation – Accumulation of tartaric and malic acid – Duration is similar for most cultivars – Berries are green due to cholorophyll BERRY DEVELOPMENT: PHASE II (40-60 DAF) • Phase II-lag phase – Slowest phase of development – Berries are firm – Berries begin to loose chlorophyll – Organic acids accumulation peaks BERRY DEVELOPMENT: PHASE III (60-120 DAF) • Phase III- Fruit softening (véraison) – Rapid berry growth (cell enlargement) – Initiation of ripening – Chlorophyll breaks down – Anthocyanins accumulate in skin (red grapes) – Sugars accumulate – Organic acids decline – Secondary metabolites accumulate Cabernet Sauvignon Flame Sauvignon blanc PROPAGATION • • • • Cuttings root easily Cut canes with three nodes (bud) Can also tip layer Be careful about propagating your own material – Royalties, quality, identity SUMMARY • Spend the time to understand the critical growth periods of the grape • Grapes are one of the most complex crops to grow • Before you grow it, be sure you know it!